The present invention is directed to electric toothbrushes, and, more particularly, to a replacement head that is attachable to an electric toothbrush drive unit.
Recognizing that toothbrush bristles require periodic replacement, manufacturers have designed replacement heads to fit onto separate drive units of electric toothbrushes. The drive units typically include a power source, switch and a drive shaft. The replacement heads typically can be removably attached to the drive units by threading or snap-fitting a portion of the replacement head onto a portion of the drive unit.
Replacement heads typically include an elongated neck with an internal brush shaft connected to a bristle bearing head. The brush shaft is arranged to transfer power from the drive shaft to the brush head for moving the brush head in a desired manner. Many brush heads are configured to convert rotational or oscillatory movement of the drive shaft about a longitudinal axis into rotational or oscillatory movement of the bristle head about an axis that is perpendicular to the longitudinal axis of the drive shaft. A variety of brush head configurations are known for providing this conversion. These brush heads commonly include multiple internal components for driving the bristle carrier and converting the motion. For example, a brush head may include a brush shaft extending within a hollow neck, a first separate drive element attached to the brush shaft aligned with the longitudinal axis of the brush head, and a second separate drive element attached to the brush shaft and offset from the longitudinal axis. One of the drive elements is connected to a bristle carrier by a gear or linkage to drive the brush head in a desired direction. Manufacturing and assembling these components can be time consuming and costly, and can lead to unwanted squeaking and rattling during operation.
Additional problems may arise with the retention of the bristle carrier on the brush head. Because the bristle carrier must be mounted for rotation and also be linked to the brush shaft to receive motion from the brush shaft, the space for structure to retain the bristle carrier on the brush head is limited. This can lead to unwanted gaps between the carrier and head, and in some cases unwanted separation of the bristle carrier.